Few sights in nature can be more romantic than that of hundreds of fireflies wafting through ghostly forest trees or low over the banks of a lake or stream on a moonless night, flashing their greeny-gold pulses of light synchronously. No childhood is complete if you haven’t caught a handful and gazed at them in wonder in your cupped palms and then let them go, winking gently into the night.
Even better, they’re not flies at all (ugh!) but beetles belonging to the lyrically named family, Lampyridae. There are around 2,000 species scattered all over the globe, and happily for us, they love warm humid climates. The rains are a good time to watch out for them, though unhappily, their numbers have suffered considerably, thanks to light pollution and what we call development.
Scientists have found two magic chemicals in their abdomens, luciferin and an enzyme luciferase, which when combined in the presence of oxygen, magnesium ions and a chemical called Adenosine triphosphate, (which apparently all of us have) give off light, with cent per cent efficiency.
How the insects switch their lights on and off remains a mystery, but each species flashes a special Morse of its own. And but naturally, the reason they do it for can only be romance. Gentlemen fireflies cruise over the bushes and undergrowth winking their lights seductively to the ladies that cluster on the foliage waiting for just their kind of guy. When a lady spots one whose flashes are long and strong, she flashes back and down he flies beside her, to deposit not only sperm but a nutrient-filled package, good for her eggs and what she’s really looking for — and what those long and strong light flashes advertised.
But sometimes there is a sinister deadly betrayal in this romance. Lady fireflies belonging to the genus Photuris pretend to be simpering ladyloves of the genus Photinus by mimicking their love signals. Gentlemen Photinus, see their signals and come flying down and instead of a date, find that they’re the dinner… (happens a lot in the insect/arthropod world). There is apparently yet another venal twist to this tale: Apparently, the sucker Photinus gents (and their ladies) have a magic chemical in their bodies called lucibufagens (LBG) which, though quite a mouthful, is unpalatable and toxic to predators. The terrible lady Photuris is after this very chemical because she doesn’t have any, and so, has no protection. So she eats poor Photinus and, in a sense, vaccinates herself with LBG, giving her insurance against predation.
And there’s yet another twist: Sometimes gentlemen Photuris (their ladies are the killers, remember) imitate the flashes of gentlemen Photinus (the suckers). Hungry for a juicy gentleman Photinus, lady Photuris flashes her acceptance to find she’s been diddled by a gentleman of her own kind, who has other things on his mind…
If you’re up in the hills or countryside at night and encounter a medley of fireflies, try and tune in on their flashes: each species flashes in a particular rhythm and pattern. Then do the same with your torch.
And do let me know what happens…
Ranjit Lal is an author, environmentalist and bird watcher
This story appeared in print under the headline Flash in the Night
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